[mythtv-users] weird problem with IR serial receiver

[Lord Darkhelmet]

Thanks for the info,  glad to hear I won't fry anything  :-)

Dean.

Richard Woelk wrote:
> Lord Darkhelmet wrote:
>   
>> I built a serial port receiver following the plans on lirc.org (and 
>> duplicated all over the place) and it did not work.   After much futzing 
>> with it, I got it to finally pick up signals but I had to change the R1 
>> pullup resister from 4k7 to 15K.   Based on the number of people who 
>> have it working as published I assume something is not right with my 
>> attempt.  With the 15k resister in place the supply voltage going to the 
>> tsop is 4.97v but the output voltage from tsop is 2.53v and drops under 
>> 2 when a button is pressed on the remote.  The motherboard is an old 
>> Asus P3V4X and the OS is FC5.  I have not tried either the stock circuit 
>> or my version on other hardware yet.   Seems to be working but I'm not 
>> sure why or if I'm risking the motherboard.  Any insight would be great.
>>
>> Dean.
>>
>>
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>>   
>>     
> Dean,
>     You won't be risking your motherboard or serial port with that mod. 
> Raising the value of the pull-up resistor will just slow the rise time 
> of the digital signal.
> Think of the IR signal closing a switch from the output line to ground, 
> the pull up resistor allows that line to rise back to 5V
> If it works, keep using it that way.
>
> The output of the tsop is a digital square wave with a rate of about 
> 4Khz, depending on the remote that is sending.
> If you can, look at it with an oscilloscope in DC mode. the wave will 
> rest at around 5V without a signal, and go to almost zero at the bottom 
> of the square wave
>
> HTH
>
> Richard
>
>
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